Need Help!- VF0 Low Voltage Alarm

[motorway]

We have a 1993 VF0, about 4 months ago there was an X axis problem, trident machine sent down someone who didnt know what they were doing, and he ended up changing every circuit board on the machine. ($10,000 Bill)

Since then we started getting the 160 alarm every once and a while, but in the last month the machine will only run for about an hour in the morning, then alarm out. Turning it off and on does nothing.

The DC buss voltage will start at around 160 then progressively drop to 120-130.
We have 208-210 volts coming in to the machine.
I checked the servo board inputs they are all getting 160v.

I tried what someone said in a post here, to disconnect each servo board and check the buss volts.
If i disconnect any one of the servo boards it will stay at 160v.

I dont understand where the machine is reading the Buss voltage from?

Thank for any help, we really need this machine running again, and cant go to trident because we still owe them 5K.

[awesome83]

There is a DC BUSS power card next to the servo drive amps, this is where the DC Buss is coming from. IF the DC buss is changing this usually the culprit. Does the measured DC Buss match the DC Buss that is displayed on the Control? (Diagnostic, then Page down once.) Here you will be able to see what the machine thinks it has for DC Buss voltage. The DC buss power card is sending a analog 0-5v signal to the MOTif board tell it how much voltage is present.
You can adjust the DC buss power card but usually what i have seen is that its a temp fix, and you'd be better changing the card. Something failed for it to change in the first place. Hope this helps.

[motorway]

I dont see any adjustments on the servo dist board(Thats what your talking about right?), actually it looks pretty different from what the haas manual shows.
I Couldn't find any point on the board with voltage that matched the number on the diagnostics screen.

I did find a capacitor with a bulged out top at the bottom of the board.
I have a feeling that most likely the problem.

Anybody have any suggestions?

[awesome83]

What is the Control Displaying for Voltage, when you have 176Vdc at the Cards?

On the older cards you can adjust a pot, but it looks like you have a newer Card and it doesn;t have anyway to adjust this. I don't usually see any problems with these cards, thats why im curious to see what the control is displaying.

[motorway]

The control shows anywhere between 127-141v when the actual voltage is between 174-179v.

What do you think about that capacitor? Could that be causing it? i just ordered a new one from digikey.

[awesome83]

I don't know what the Cap is for. and haas doesn't give out schematics...
Either there is something wrong with the power PCB or the Motif that monitors the voltage at the power PCB.

[amplexus]

If you are just voltage dropping under load it should be easy enough to chase down, and for a lot less then 10 grand. Board swappers tend to be useless. Is it just a simple linear power supply or a switcher? If it is linear it could well be the filter cap. Can you post a schematic?
Amplexus Ender

[awesome83]

The control is looking for 145-175 range for DC buss voltage. It's not the output of the power supply, its the monitoring of the voltage. You have the correct voltage out put, possibly too high, but the control thinks you only have 125-147, hence the alarm. You can trace the cable that goes to p17 on the motif board, checking the connections, ect.

[ITT-Student]

That capacitor definitly appears bad and can cause intermitent problems as they get warm and charged. Definitly change that "bulged" cap!
Does the capacitor appear to be linked to the alarm circuit? And if you change one cap it is best just to change them all.

[motorway]

I put in 2 new caps on the board today, the voltage doesn't fluctuate like it use to, steady at 169v.
But the real test wont be until monday when its running.

Thanks for all the help!

[ITT-Student]

Please let me know if this solves your problem my friend, and feel free to contact me for any advice or support or even to research an issue you might be having, purely for my learning experience and to be of assistance.

Good Luck,
jjaeger110@email.itt-tech.edu

[ITT-Student]

Oh yeah, could there be a possiblity your boards are'nt properly cooled? A hot shop environment is definitely a suspect to intermitent issues.